Positive electrode composite material for lithium ion secondary battery and use thereof

ABSTRACT

A positive electrode composite material for a lithium ion secondary battery that makes it possible to appropriately reduce the electric resistance in a positive electrode and to realize a high-performance lithium ion secondary battery. The positive electrode composite material to be used in the positive electrode of the lithium ion secondary battery includes a particulate positive electrode active material composed of a lithium composite oxide having a layered crystal structure including at least lithium, and a conductive oxide. Here, a particulate region where primary particles of the conductive oxide are aggregated, and a film-shaped region where the conductive oxide is formed in a film shape adhere to at least a part of the surface of the positive electrode active material. The average particle diameter based on cross-sectional TEM observation of primary particles in the particulate region is equal to or greater than 0.3 nm, and in cross-sectional TEM observation of the film-shaped region, no particles with a particle diameter equal to or greater than 0.3 nm are observed, and there are no voids equal to or greater than 2 nm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2018/004450 filed Feb. 8, 2018, claiming priority based onJapanese Patent Application No. 2017-022417 filed on Feb. 9, 2017, theentire contents of that application being incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a positive electrode composite materialfor a lithium ion secondary battery that is suitable for a positiveelectrode of a lithium ion secondary battery, and to a lithium ionsecondary battery using the positive electrode composite material.

BACKGROUND ART

In recent years, secondary batteries such as lithium ion secondarybatteries and nickel hydrogen batteries have been advantageously used asso-called portable power sources for personal computers and portableterminals and also as power sources for driving vehicles. In particular,lithium ion secondary batteries, which are light in weight and capableof obtaining high energy density, are becoming increasingly important ashigh-power power sources to be mounted on vehicles such as electricvehicles and hybrid vehicles.

Such a lithium ion secondary battery uses, for example, a positiveelectrode in which a positive electrode composite material layer isprovided on the surface of a positive electrode current collector thatis a conductive foil. The positive electrode composite material layerincludes a positive electrode active material composed of a lithiumcomposite oxide that occludes and releases lithium ions. The positiveelectrode composite material layer is formed of a paste-like positiveelectrode composite material for a lithium ion secondary battery(hereinafter, also simply referred to as “positive electrode compositematerial”) in which a positive electrode active material and otheradditives are dispersed in a dispersion medium.

The additive to be added to this positive electrode composite materialcan be exemplified by a conductive oxide. By adding the conductiveoxide, an electron path can be formed with the positive electrode activematerial to reduce the electrical resistance in the positive electrode.For example, Patent Literature 1 discloses a cathode (positiveelectrode) in which a cathode active material composition (positiveelectrode composite material layer) is coated with vanadium oxide(conductive oxide). Further. Patent Literature 2 discloses a techniqueof adding an oxide represented by the general formula: ABO₃, A₂BO₄, MO₂or a mixture of such oxides to a positive electrode. In addition, PatentLiterature 3 discloses a non-aqueous electrolyte secondary battery inwhich the surface of the active material particles contained in thepositive electrode is coated with an oxide represented by the generalformula: ABO₃ or A₂BO₄.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application Publication No.    2009-76446-   Patent Literature 2: Japanese Patent Application Publication No.    2000-235858-   Patent Literature 3: Japanese Patent Application Publication No.    2001-266879

SUMMARY OF INVENTION Technical Problem

However, it cannot be said that the techniques described in PatentLiteratures 1 to 3 described above can sufficiently reduce theelectrical resistance in the positive electrode, and further improvementhas been desired.

For example, as a result of examining the technique described in PatentLiterature 1, the inventors of the present invention have found thatwith such a technique, the surface of the positive electrode compositematerial layer is coated with particulate vanadium oxide having lowdensity low density, and a sufficient electron path cannot be formedbecause of point contact between the vanadium oxide and the positiveelectrode active material.

Further, in the technique described in Patent Literature 2, aparticulate conductive oxide is dispersed in the positive electrodecomposite material layer, and a point contact is realized between theparticulate positive electrode active material and the conductive oxidein the same manner as in the above-described Patent Literature 1.

Meanwhile, in the technique described in Patent Literature 3, since athin film of conductive oxide is formed on the surface of theparticulate positive electrode active material, a wider electron pathcan be formed as compared with the technique using a particulateconductive oxide as in Patent Literature 1 or Patent Literature 2.However, the research conducted by the inventors of the presentinvention has demonstrated that with the technique of Patent Literature3, a new problem arises. Thus, since the abovementioned conductive oxideand positive electrode active material are sintered to form a composite,the area of the contact portion between the positive electrode activematerial and the electrolyte is significantly reduced and the reactionresistance is increased.

The present invention has been completed with the foregoing in view, andthe main object thereof is to provide a positive electrode compositematerial for a lithium ion secondary battery that makes it possible toreduce appropriately the electrical resistance in a positive electrodeand to realize a high-performance lithium ion secondary battery.

Solution to Problem

In order to achieve the above object, the present invention provides apositive electrode composite material for a lithium ion secondarybattery having the following configuration.

The positive electrode composite material for a lithium ion secondarybattery disclosed herein is a positive electrode composite material tobe used for a positive electrode of a lithium ion secondary battery, thepositive electrode composite material including a particulate positiveelectrode active material composed of a lithium composite oxide having alayered crystal structure including at least lithium, and a conductiveoxide.

Here, in such a positive electrode composite material for a lithium ionsecondary battery, a particulate region where primary particles of theconductive oxide are aggregated, and a film-shaped region where theconductive oxide is formed in a film shape adhere to at least a part ofthe surface of the positive electrode active material, an averageparticle diameter based on cross-sectional TEM observation of primaryparticles in the particulate region is equal to or greater than 0.3 nm,and in cross-sectional TEM observation of the film-shaped region, noparticles with a particle diameter equal to or greater than 0.3 nm areobserved, and no voids equal to or greater than 2 nm are observed.

In the positive electrode composite material disclosed herein, theparticulate region where primary particles of the conductive oxide areaggregated, and the film-shaped region where the conductive oxide isformed in a film shape adhere to at least a part of the surface of thepositive electrode active material.

In such a positive electrode composite material, the film-shaped regioncomposed of the conductive oxide adheres to the positive electrodeactive material in a very dense state in which particles equal to orgreater than 0.3 nm and voids equal to or greater than 2 nm are notrecognized. Therefore, surface contact with the surface of the positiveelectrode active material can form a wide electron path, and theresistance in the positive electrode can be greatly reduced.

Meanwhile, the particulate region of the positive electrode compositematerial is formed by the aggregation of relatively large primaryparticles having an average particle diameter equal to or greater than0.3 nm. As a result, the primary particles and the positive electrodeactive material come into point contact with each other at a locationwhere the particulate region on the surface of the positive electrodeactive material adheres, and thus an electron path is formed at thecontact point, the surface of the positive electrode active material isexposed in portions other than the contact point, and sufficient area ofcontact between the positive electrode active material and theelectrolyte can be ensured. For this reason, an increase in reactionresistance due to a decrease in the contact area between the positiveelectrode active material and the electrolyte can be suppressed.

As described above, with the positive electrode composite materialdisclosed herein, a wide electron path can be formed at a location wherethe particulate region on the surface of the positive electrode activematerial adheres, thereby significantly reducing the resistance in thepositive electrode. In addition, since a sufficient contact area betweenthe positive electrode active material and the electrolyte can beensured at the location where the particulate region adheres and theincrease in reaction resistance can be suppressed, the batteryperformance can be significantly improved as compared to theconventional positive electrode composite material.

Further, in a preferred embodiment of the positive electrode compositematerial disclosed herein, the conductive oxide is a metal oxiderepresented by a general formula (1):MO₂  (1)(where, M in the formula (1) above is one or two or more elementsselected from transition metal elements of groups Va, VIa, VIIa, VIII,and Ib), or a metal oxide having a perovskite structure and representedby a general formula (2):ABO₃  (2)(where, A in the formula (2) above is one or two or more elementsselected from the group consisting of divalent typical elements,lanthanoid elements, and a combination thereof, and B is one or two ormore elements selected from transition metal elements of groups IVa, Va,VIa, VIIa, VIII, and Ib).

The metal oxide represented by MO₂ in the general formula (1) above andthe metal oxide ABO₃ having a perovskite structure and represented bythe general formula (2) above form a suitable electron path with thepositive electrode active material. Therefore, the resistance in thepositive electrode can be reduced more appropriately to improve thebattery performance more suitably.

Further, in another preferable embodiment of the positive electrodecomposite material disclosed herein, the conductive oxide is rutheniumoxide or a lanthanum manganese cobalt composite oxide.

Among the metal oxides represented by the general formula (1) or thegeneral formula (2) above, the ruthenium oxide and lanthanum manganesecobalt composite oxide can reduce the resistance in the positiveelectrode particularly suitably. Therefore, the performance of theconstructed lithium ion secondary battery can be improved more suitably.

In yet another preferable embodiment of the positive electrode compositematerial disclosed herein, the positive electrode active material is alithium composite oxide represented by a general formula (3):Li_(1+α)Ni_(x)Co_(y)Mn_(z)M_(β)O_(2−γ)A_(γ)  (3)(where, M in the formula (3) above is one or two or more elementsselected from the group consisting of Zr, Mo, W, Mg, Ca, Na, Fe, Cr, Zn,Si, Sn, Al, and B; A in the formula (3) is one or two or more elementsselected from the group consisting of F, Cl, and Br; and x, y, z, α, β,and γ is 0≤α≤0.7, 0≤x<0.9, 0≤y<0.4, x+y+z≈1, 0≤β≤0.1, 0≤γ≤0.5,respectively).

The lithium composite oxide as represented by the general formula (3)has high ion conductivity, and therefore can contribute to theconstruction of a high-energy-density battery, and also excels inthermal stability, and therefore can contribute to the improvement ofbattery durability.

Further, in another preferable embodiment of the positive electrodecomposite material disclosed herein, a coverage based on cross-sectionalTEM observation of the conductive oxide on the surface of the positiveelectrode active material is 11% to 40%.

Where the coverage of the conductive oxide is too high, the contact areabetween the positive electrode active material and the electrolyte maybe reduced, whereas when the coverage is too low, a sufficient electronpath cannot be formed. In the present embodiment, with theaforementioned findings in view, the coverage based on cross-sectionalTEM observation of the conductive oxide on the surface of the positiveelectrode active material is set to 11% to 40%, thereby ensuringsufficient contact area between the positive electrode active materialand the electrolyte and forming a sufficient electron path. Therefore,the battery performance can be more appropriately improved.

In another preferable embodiment of the positive electrode compositematerial disclosed herein, an average particle diameter based oncross-sectional TEM observation of the particulate region is 0.6 nm to55 nm, and a film thickness based on cross-sectional TEM observation ofthe film-shaped region is 0.5 nm to 50 nm.

As a result of various experiments and studies conducted by theinventors of the present invention, it has been found that in thepositive electrode composite material disclosed herein, the averageparticle diameter of the particulate region and the film thickness ofthe film-shaped region exert significant influence on the batteryperformance (normalized battery resistance) of a lithium ion secondarybattery. Additional experiments have demonstrated that by setting theaverage particle diameter of the particulate region to 0.6 nm to 55 nmand setting the film thickness of the film-shaped region to 0.5 nm to 50nm, it is possible to construct a high-performance lithium ion secondarybattery having a low normalized battery resistance. This embodiment isbased on such findings.

Moreover, in another preferable embodiment of the positive electrodecomposite material disclosed herein, at least parts of the particulateregion and the film-shaped region are in contact with each other.

By so bringing the particulate region and the film-shaped region intocontact with each other, a sufficient electron path can be formed at thecontact portion, and the contact area between the positive electrodeactive material and the electrolyte can be appropriately ensured.Therefore, the battery performance can be improved more suitably.

According to another aspect of the present invention, there is provideda lithium ion secondary battery in which a positive electrode compositematerial layer is produced using the above-described positive electrodecomposite material. Specifically, the lithium ion secondary batteryincludes: a positive electrode having a positive electrode compositematerial layer applied to a positive electrode current collector, anegative electrode having a negative electrode composite material layerapplied to a negative electrode current collector, and a non-aqueouselectrolyte, wherein the positive electrode composite material layerincludes a particulate positive electrode active material composed of alithium composite oxide having a layered crystal structure including atleast lithium, and a conductive oxide.

Further, in the lithium ion secondary battery disclosed herein, aparticulate region where primary particles of the conductive oxide areaggregated, and a film-shaped region where the conductive oxide isformed in a film shape adhere to at least a part of the surface of thepositive electrode active material, an average particle diameter basedon cross-sectional TEM observation of primary particles in theparticulate region is equal to or greater than 0.3 nm, and incross-sectional TEM observation of the film-shaped region, no particleswith a particle diameter equal to or greater than 0.3 nm are observed,and there are no voids equal to or greater than 2 nm.

In the lithium ion secondary battery disclosed herein, the positiveelectrode composite material layer is formed using the positiveelectrode composite material in which the particulate region and thefilm-shaped region composed of a conductive oxide adhered to a part ofthe surface of the positive electrode active material. For this reason,the resistance in the positive electrode is appropriately reduced, andthe increase in reaction resistance in the positive electrode issuppressed. As a result, battery performance superior to that of therelated art can be exhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional TEM image of a positive electrode compositeaccording to an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing the outer shape of alithium ion secondary battery.

FIG. 3 is a perspective view schematically showing an electrode body ofa lithium ion secondary battery.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be describedwith reference to the drawings. In the following drawings, the samereference numerals are given to members and portions that exhibit thesame action. Also, the dimensional relationships (length, width,thickness, etc.) in the drawings do not reflect the actual dimensionalrelationships. In addition, matters other than those specificallymentioned in the present description and necessary for implementing thepresent invention (for example, configuration and manufacturing methodof negative electrode and electrolyte, general techniques relating toconstruction of lithium ion secondary battery, etc.) can be understoodas design matters for a person skilled in the art which are based on theconventional techniques in the pertinent field.

1. Positive Electrode Composite Material for Lithium Ion SecondaryBattery

FIG. 1 is a cross-sectional TEM image of a positive electrode compositematerial according to the present embodiment. As shown in FIG. 1, thepositive electrode composite material according to the presentembodiment includes a positive electrode active material 1 and aparticulate region 2 a and a film-shaped region 2 b composed of aconductive oxide. Each of these will be specifically described below.

(1) Positive Electrode Active Material

The positive electrode active material 1 in the present embodiment isconfigured of a lithium composite oxide having a layered crystalstructure including at least lithium. The positive electrode activematerial 1 in the present embodiment has a particulate shape, and FIG. 1is a cross-sectional TEM image in which the vicinity of the surface ofthe particulate positive electrode active material is enlarged. Theaverage particle diameter based on the cross-sectional TEM image of theparticulate positive electrode active material 1 is about 1 μm to 20 μm(preferably 2 μm to 10 μm).

The lithium composite oxide constituting this positive electrode activematerial 1 can be exemplified by a lithium nickel composite oxide, alithium nickel cobalt composite oxide, a lithium nickel cobalt manganesecomposite oxide and the like. Among these lithium composite oxides, alithium composite oxide represented by the following general formula (3)is preferable. The lithium composite oxide represented by the followinggeneral formula (3) has high ion conductivity, so that the energydensity of the constructed lithium ion secondary battery can beincreased, and because such lithium composite oxide excels in thermalstability, the durability can also be improved.Li_(1+α)Ni_(x)Co_(y)Mn_(z)MpO_(2−γ)A_(γ)  (3)where, M in the general formula (3) above is one or two or more elementsselected from the group consisting of Zr, Mo. W. Mg, Ca, Na, Fe. Cr, Zn.Si, Sn. Al, and B; A in the formula (3) is one or two or more elementsselected from the group consisting of F, Cl, and Br; and x, y, z, α, β,and γ is 0≤α≤0.7, 0≤x<0.9, 0≤y<0.4, x+y+z≈1, 0≤β≤0.1, 0≤γ≤0.5,respectively.

(2) Conductive Oxide

(a) Composition of Conductive Oxide

As described above, the positive electrode composite material accordingto the present embodiment includes a conductive oxide. As the conductiveoxide in the present invention, it is preferable to use, for example, ametal oxide represented by the following general formula (1).MO₂  (1)

In the general formula (1) above. M is one or two or more elementsselected from transition metal elements of groups Va, VIa, VIIa, VIII,and Ib.

Specific examples of the metal oxide represented by MO₂ of the generalformula (1) above include ruthenium dioxide (RuO₂), vanadium dioxide(VO₂), chromium dioxide (CrO₂), molybdenum dioxide (MoO₂), tungstendioxide (WO₂), rhenium dioxide (ReO₂), niobium dioxide (NbO₂), rhodiumdioxide (RhO₂), iridium dioxide (IrO₂), palladium dioxide (PdO₂),platinum dioxide (PtO₂), osmium dioxide (OsO₂) and the like.

Also, in addition to the metal oxide represented by the general formula(1) above, a metal composite oxide of a perovskite structure representedby the following general formula (2) may be used as the conductiveoxide.ABO₃  (2)

In the general formula (2) above. A is one or two or more elementsselected from the group consisting of divalent typical elements,lanthanoid elements, and a combination thereof.

Further, B in the general formula (2) is one or two or more elementsselected from transition metal elements of groups IVa, Va, VIa, VIIa.VIII, and Ib.

As the metal composite oxide ABO₃ of the general formula (2), forexample, a lanthanum manganese cobalt composite oxide (for example,LaMn_(0.5)Co_(0.5)O₃), lanthanum nickel composite oxide (LaNiO₃),strontium vanadate (SrVO₃), calcium vanadate (CaVO₃), strontium ferrate(SrFeO₃), lanthanum titanate (LaTiO₃), strontium chromate (SrCrO₃),calcium chromate (CaCrO₃), calcium ruthenate (CaRuO₃), strontiumruthenate (SrRuO₃), strontium iridate (SrIrO₃) or the like may be used.

Moreover, a metal composite oxide having a composition other than thatshown by the general formula (1) and general formula (2) can also beused for the conductive oxide. Such a metal composite oxide can beexemplified by lanthanum strontium nickel composite oxide (LaSrNiO₄).

The metal oxide represented by the general formula (1) or the generalformula (2) described above can appropriately form an electron path withthe positive electrode active material, and appropriately reduce theresistance in the positive electrode. Among the specific examplesdescribed above, ruthenium dioxide and lanthanum manganese cobaltcomposite oxide can reduce the resistance in the positive electrodeparticularly appropriately.

(b) Structure of Conductive Oxide

As shown in FIG. 1, in the positive electrode composite materialaccording to the present embodiment, a particulate region 2 a whereprimary particles of the conductive oxide are aggregated and thefilm-shaped region 2 b where the conductive oxide is formed in a filmshape adhere to at least a part of the surface of the positive electrodeactive material 1.

As described above, the particulate region 2 a is formed by theaggregation of primary particles of the conductive oxide, and theaverage particle diameter based on cross-sectional TEM observation ofsuch primary particles is 0.3 nm or more, preferably 0.3 nm to 15 nm,and more preferably 1 nm to 10 nm. The particulate region 2 aconstituted by the primary particles of the conductive oxide having arelatively large particle diameter in this manner is in point contactwith the surface of the positive electrode active material 1. Therefore,an electron path can be formed at the contact point between theparticulate region 2 a and the positive electrode active material 1, andthe surface of the positive electrode active material 1 is exposed atportions other than the contact point, thereby making it possible toensure a wide contact area of the positive electrode active material 1and the electrolyte.

The film-shaped region 2 b is a portion appearing white in thecross-sectional TEM image shown in FIG. 1. The film-shaped region 2 b isa region where the conductive oxide is formed in a film shape so as tocover the surface of the positive electrode active material 1. Althoughdescribed hereinbelow in detail, the film-shaped region 2 b in thepresent embodiment is constituted by a conductive oxide which has notbeen subjected to a crystallization process such as calcination, bycontrast with the conductive oxides used in general lithium ionsecondary batteries. Further, the film-shaped region 2 b has a verydense structure in which, in cross-sectional TEM observation, no primaryparticles with a particle diameter equal to or greater than 0.3 nm arepresent, and no voids equal to or greater than 2 nm are present. Sincethe film-shaped region 2 b is in surface contact with the surface of thepositive electrode active material 1 and has a dense structure in whichlarge primary particles and voids are not present, a wide electron pathcan be formed with the positive electrode active material 1.

Thus, in the positive electrode composite material according to thepresent embodiment, since the particulate region 2 a and the film-shapedregion 2 b adhere as a mixture to a part of the surface of the positiveelectrode active material 1, a wide electron path can be formed at alocation where the film-shaped region 2 b has adhered, so that theresistance in the positive electrode can be significantly reduced, andthe surface of the positive electrode active material 1 is appropriatelyexposed at a location where the particulate region 2 a has adhered, sothat sufficient contact area with the electrolyte can be ensured.Therefore, by forming the positive electrode of the lithium ionsecondary battery by using the positive electrode composite materialaccording to the present embodiment, it is possible to obtain ahigh-performance lithium ion secondary battery having batteryperformance that is significantly improved as compared with the relatedart.

Furthermore, when the positive electrode composite material according tothe present embodiment is used, lithium ions are easily desorbed fromthe electrolyte, so that the speed of the electrode reaction at thepositive electrode is increased over the conventional one to furtherimprove the battery performance. This is understood to be because theelectron density is different between the particulate region 2 a and thefilm-shaped region 2 b, and two types of conductive oxides different inthe electron density are caused to adhere to the surface of the positiveelectrode active material, thereby making it possible to destabilize thestructure of solvated lithium supplied from the electrolyte and reducethe activation energy in the desolvation process.

Further, the coverage based on cross-sectional TEM observation of thesurface of the positive electrode active material 1 at the surface ofthe positive electrode active material 1 is preferably 0.9% to 51%, andmore preferably 11% to 40%. By setting the coverage of the conductiveoxide in this manner, sufficient contact area between the positiveelectrode active material and the electrolyte can be ensured, and asufficient electron path can be formed, thereby making it possible toimprove the battery performance appropriately.

In addition, as a result of conducting various experiments and studieson the positive electrode composite material according to the presentembodiment, the inventors of the present invention have found that thebattery performance is greatly influenced by the average particlediameter of the particulate region 2 a and the film thickness of thefilm-shaped region 2 b. Specifically, by setting the average particlediameter based on cross-sectional TEM observation of the particulateregion 2 a to 0.3 nm to 60 nm (preferably 0.6 nm to 55 nm), and settingthe film thickness based on cross-sectional TEM observation of thefilm-shaped region 2 b to 0.2 nm to 55 nm (preferably 0.5 nm to 50 nm),it is possible to construct a high-performance lithium ion secondarybattery in which the normalized battery resistance is greatly reduced.

The area ratio of the film-shaped region 2 b to the particulate region 2a in the cross-sectional TEM observation is preferably 0.2% to 50%. Byusing the positive electrode composite material in which the particulateregion 2 a and the film-shaped region 2 b are present at such a ratio,the resistance in the positive electrode can be more suitably reduced toobtain high battery performance.

Further, it is preferable that 90% of primary particles among theplurality of primary particles constituting the particulate region 2 abe present within 1.5 μm from the contact point between the particulateregion 2 a and the positive electrode active material 1. As a result,the electron path between the particulate region 2 a and the positiveelectrode active material 1 can be formed more appropriately, therebymaking it possible to reduce appropriately the resistance in thepositive electrode.

Moreover, it is preferable that that the regions be formed so that atleast parts of the particulate region 2 a and the film-shaped region 2 bbe in contact with each other as shown in FIG. 1. By bringing theparticulate region 2 a and the film-shaped region 2 b into contact witheach other in such a manner, a sufficient electron path can be formed inthe contact portion of these regions, and the contact area between thepositive electrode active material and the electrolyte can beappropriately ensured. Therefore, the battery performance can beimproved more suitably.

2. Method for Manufacturing Positive Electrode Composite Material forLithium Ion Secondary Battery

Next, a method for manufacturing the positive electrode compositematerial according to the above-described embodiment will be described.

(1) Production of Positive Electrode Active Material

The positive electrode active material can be produced through the sameprocess as a positive electrode active material for a general lithiumion secondary battery. Specifically, an aqueous solution is prepared byweighing supply sources (raw materials) of metal elements other than Liso as to have a desired composition ratio and mixing the weighed supplysources with an aqueous solvent. As supply sources of the metal elementsother than Li, for example, sulfates of additional metal elements suchas Ni, Co, Mn and the like (nickel sulfate: NiSO₄, cobalt sulfate:CoSO₄, manganese sulfate: MnSO₄, and the like) may be used.

Next, the aqueous solution is neutralized by adding a basic aqueoussolution (such as an aqueous sodium hydroxide solution) while stirringthe prepared aqueous solution. As a result, the hydroxides of theabove-mentioned additional metal elements precipitate, and a sol-likeraw material hydroxide (precursor) can be obtained.

Then, a predetermined amount of lithium source (lithium carbonate,lithium hydroxide, lithium nitrate, and the like) is mixed with theobtained sol-like precursor, and then calcination is performed at 700°C. to 1000° C. (for example, 900° C.) for 1 h to 20 h (for example, 15h) under an oxidizing atmosphere. By pulverizing the calcined body thusobtained to a desired particle diameter (for example, an averageparticle diameter of 10 μm), a particulate positive electrode activematerial composed of a lithium composite oxide having a layered crystalstructure can be obtained.

(2) Adhesion of Conductive Oxide

In the manufacturing method according to the present embodiment, atleast a part of the surface of the positive electrode active materialobtained as described above, a particulate region where primaryparticles of the conductive oxide are aggregated, and a film-shapedregion where the conductive oxide is formed in a film shaped are adheredto at least part of the surface of the positive electrode activematerial thus obtained.

Specifically, an alkoxide (for example, ruthenium alkoxide) of a mainmetal element of the conductive oxide (M in the general formula (1)above or A and B in the general formula (2)) is mixed and stirred withthe positive electrode active material, and the mixture is dried at apredetermined temperature. After the alkoxide of the metal element isthus decomposed, the metal element is oxidized to form a conductiveoxide, and the film-shaped conductive oxide adheres to the surface ofthe positive electrode active material. At this time, in the presentembodiment, by contrast with the conventional technique, sincecrystallization treatment such as calcination is not performed afterdrying, a film-shaped region in which the conductive oxide is denselyformed can be adhered to the surface of the positive electrode activematerial. The drying temperature in this step is preferably set to atemperature at which the conductive oxide does not crystallize, that is,200° C. to 450° C. (for example, 400° C.).

In the present embodiment, next, the particulate region is caused toadhere to the positive electrode active material having the film-shapedregion adhered to the surface. Specifically, mechanochemical treatmentis performed after the powder of the positive electrode active materialto which the film-shaped region has adhered and the powder of theconductive oxide are mixed. In the case of using a general mechanofusionapparatus (for example, NOBILTA MINI manufactured by Hosokawa MicronCorporation), it is preferable that the treatment temperature of themechanochemical treatment be normal temperature (for example, 15° C. to35° C.), the load power be 0.1 kW to 1.0 kW (for example, 0.5 kW), andthe treatment time be set to 1 min to 10 min (for example, 3 min).

By so mixing the powder of the positive electrode active material towhich the film-shaped region has adhered and the powder of theconductive oxide and performing mechanochemical treatment, mechanicalenergy is imparted to each particle. Therefore, the film-shaped regionand the particulate region in which primary particles of the conductiveoxide have aggregated can be adhered to at least a part of the surfaceof the positive electrode active material.

(3) Preparation of Positive Electrode Composite Material

The positive electrode composite material according to the presentembodiment can be produced by dispersing the composite material of thepositive electrode active material and the conductive oxide obtained asdescribed above in a predetermined dispersion medium, and thenappropriately adding other additives. As the dispersion medium and theother additives, those suitable for general lithium ion secondarybatteries may be used without any particular limitation, and the presentinvention is not characterized thereby. Therefore, the descriptionthereof is herein omitted.

3. Lithium Ion Secondary Battery

Next, a lithium ion secondary battery having a positive electrodeproduced using the positive electrode composite material according tothe above-described embodiment will be specifically described. A lithiumion secondary battery provided with a wound electrode assembly isdescribed below as an example, but such a configuration is not intendedto limit the usage mode of the present invention. For example, thepositive electrode active material of the present invention can also beused in a stacked electrode body in which a plurality of positiveelectrodes and negative electrodes is alternately stacked.

FIG. 2 is a perspective view schematically showing the outer shape of alithium ion secondary battery. A lithium ion secondary battery 100 isconfigured by housing an electrode body (not shown) inside an angularcase 50 shown in FIG. 2.

(1) Case

A case 50 is composed of a flat case main body 52 having an open upperend and a lid 54 for closing the opening at the upper end. The lid 54 isprovided with a positive electrode terminal 70 and a negative electrodeterminal 72. Although not shown, the positive electrode terminal 70 iselectrically connected to the positive electrode of the electrode bodyin the case 50, and the negative electrode terminal 72 is electricallyconnected to the negative electrode.

(2) Electrode Body

Next, the electrode body housed inside the above-described case 50 isexplained. FIG. 3 is a perspective view schematically showing anelectrode body of a lithium ion secondary battery. The electrode body inthe present embodiment is a wound electrode body 80 produced bylaminating and winding long sheet-shaped positive electrode 10 andnegative electrode 20 together with a long sheet-shaped separator 40 asshown in FIG. 3.

(a) Positive Electrode

In the positive electrode 10 in FIG. 3, a positive electrode compositematerial layer 14 including a positive electrode active material isapplied to both surfaces of a long sheet-like positive electrode currentcollector 12. A positive electrode composite material layernon-formation portion 16 that is not coated with the positive electrodecomposite material layer 14 is formed at one side edge portion in thewidth direction of the positive electrode 10. This positive electrodecomposite material layer non-formation portion 16 is electricallyconnected to the positive electrode terminal 70 (see FIG. 2) describedabove.

The positive electrode composite material layer 14 in the presentembodiment is formed of the positive electrode composite material havingthe above-described configuration. Specifically, after the positiveelectrode composite material according to the above-described embodimentis applied to both surfaces of the positive electrode current collector12 and dried, the positive electrode composite material layer 14 isformed by pressing with a predetermined pressure.

In the positive electrode composite material layer 14, the particulateregion 2 a where the primary particles of the conductive oxide areaggregated and the film-shaped region 2 b where the conductive oxide isformed in a film shape adhere to at least a part of the surface of thepositive electrode active material 1 (see FIG. 1). By forming such apositive electrode composite material layer 14, the resistance of thepositive electrode 10 can be reduced and the battery performance can beimproved.

(b) Negative Electrode

In the negative electrode 20, similarly to the positive electrode 10,the negative electrode composite material layer 24 mainly composed ofthe negative electrode active material is applied to both surfaces ofthe long sheet-shaped negative electrode current collector 22. Then, anegative electrode composite material layer non-formation portion 26 isformed at one side edge portion in the width direction of the negativeelectrode 20, and this negative electrode composite material layernon-formation portion 26 is electrically connected to the negativeelectrode terminal 72 (see FIG. 1).

The material of the negative electrode active material in the presentembodiment is not particularly limited, and any of various materialsthat may be used as a negative electrode active material of a generallithium ion secondary battery may be used singly or in combination(mixture or composite) of two or more thereof. Preferred examples ofsuch negative electrode active materials include carbon materials suchas graphite, non-graphitizable carbon (hard carbon), graphitizablecarbon (soft carbon), carbon nanotubes, or materials structured of acombination of these. Among them, graphite-based materials (naturalgraphite (graphite), artificial graphite and the like) can be preferablyused from the viewpoint of energy density.

Further, the negative electrode active material is not limited to theabove-mentioned carbon-based material, and for example, lithium titaniumcomposite oxides such as Li₄Ti₅O₁₂ and lithium composite oxides such aslithium transition metal composite nitrides may be used. In addition,various additives suitable for general lithium ion secondary batteriescan be added, as required, to the negative electrode composite materiallayer 24 in the same manner as to the positive electrode compositematerial layer 14.

(c) Separator

The separator 40 is disposed so as to be interposed between the positiveelectrode 10 and the negative electrode 20 described above. Aband-shaped sheet material having a predetermined width and having aplurality of minute holes is used as the separator 40. The material ofthe separator 40 can be the same as that used in a general lithium ionsecondary battery, and for example, a porous polyolefin resin or thelike may be used.

(4) Electrolyte

Further, the same electrolyte (for example, non-aqueous electrolyticsolution) as that suitable for a general lithium ion secondary batterymay be used without any particular limitation as the electrolyte housedin the case 50 together with the wound electrode body 80 describedabove. As a specific example, a nonaqueous electrolytic solutionincluding LiPF₆ at a concentration of about 1 mol/L in a mixed solventof ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methylcarbonate (EMC) (for example, volume ratios 3:4:3) may be used.

4. Construction of Lithium Ion Secondary Battery

In constructing a lithium ion secondary battery provided with theabove-described members, first, the wound electrode body 80 is housed inthe case main body 52, and the electrolyte is filled (poured) in thecase main body 52. Thereafter, the electrode terminals 70 and 72provided at the lid 54 are connected to the positive electrode compositematerial layer non-formation portion 16 and the negative electrodecomposite material layer non-formation portion 26 of the wound electrodebody 80, and then the opening at the upper end of the case main body 52is sealed with the lid 54. A lithium ion secondary battery 100 is thusconstructed.

In the lithium ion secondary battery 100 constructed in this manner,since the electron path is sufficiently formed by the conductive oxidein the positive electrode composite material layer 14 of the positiveelectrode 10, the resistance in the positive electrode 10 issignificantly reduced. Since the sufficient contact area between thepositive electrode active material and the electrolyte can be ensured,the increase in reaction resistance caused by coating the positiveelectrode active material with the conductive oxide can be appropriatelysuppressed. Furthermore, with such a lithium ion secondary battery 100,it is possible to facilitate the desorption of lithium ions from theelectrolyte and to make the speed of the electrode reaction in thepositive electrode higher than that in the related art. As describedabove, according to the present embodiment, it is possible to provide alithium ion secondary battery in which various types of batteryperformance are improved as compared with the related art.

TEST EXAMPLES

Hereinafter, test examples relating to the present invention aredescribed, but the description of the test examples is not intended torestrict the present invention.

In the test examples, the following tests A to C were conducted toinvestigate the types of effects produced on battery performance when alithium ion secondary battery is constructed using a positive electrodecomposite material in which a particulate region and a film-shapedregion composed of a conductive oxide are adhered to a part of thesurface of a positive electrode active material.

1. Test A

(1) Test Examples 1 to 5

Positive electrodes were produced using different positive electrodecomposite materials in each of Test Examples 1 to 5, and lithium ionsecondary batteries for evaluation tests were constructed using thepositive electrodes.

Specifically, as shown in Table 1, in Test Example 1, ruthenium dioxide(RuO₂) was used as the conductive oxide, and the positive electrodecomposite material in which the particulate region and the film-shapedregion composed of the RuO₂ adhered to the surface of the positiveelectrode active material was used. A method for causing the particulateregion and the film-shaped region to adhere to the surface of thepositive electrode active material was performed according to the“Adhesion of Conductive Oxide” section described hereinabove. At thistime, the amount (mol) of the conductive oxide used in the film-shapedregion and the amount of the conductive oxide used in the particulateregion are equal to each other, and the amount of the conductive oxideused was adjusted such that the total weight of the Ru element containedin the film-shaped region and the particulate region was 0.5 wt %.

Further, in Test Example 2, a positive electrode composite material wasused in which only the film-shaped region composed of RuO₂ adhered tothe surface of the positive electrode active material. In Test Example3, a positive electrode composite material was used in which only theparticulate region composed of RuO₂ adhered to the surface of thepositive electrode active material. In Test Example 4, as a comparisonobject, a positive electrode composite material was used to which aconductive oxide was not added. Other conditions of Test Examples 2 to 4were set to the same conditions as in Test Example 1.

Furthermore, in Test Example 5, a positive electrode composite materialwas used in which a lanthanum manganese cobalt composite oxide(LaMn_(0.5)Co_(0.5)O₃) was used as the conductive oxide, and theparticulate region and the film-shaped region composed of theLaMn_(0.5)Co_(0.5)O₃ adhered to the surface of the positive electrodeactive material. Other conditions of Test Example 5 were set to the sameconditions as in Test Example 1.

In Test Examples 1 to 5, lithium nickel cobalt manganese composite oxide(LiNi_(0.33)Co_(0.33)Mn_(0.33)O₂) was used as a positive electrodeactive material. In addition, in each of Test Examples 1 to 3 and TestExample 5, the coverage of the conductive oxide was set to 11%.

(2) Construction of Lithium Ion Secondary Battery for Evaluation Tests

The procedure of constructing a lithium ion secondary battery forevaluation tests will be specifically described hereinbelow.

(a) Production of Positive Electrode

Positive electrodes were manufactured, as described above, by usingpositive electrode composite materials that differed in Test Examples 1to 5. Specifically, a composite material of a positive electrode activematerial and a conductive oxide was prepared in each of Test Examples 1to 5, and the composite material was dispersed in a dispersion medium(NMP: N-methvlpyrrolidone), and then a binder (PVDF) and a conductiveaid (acetylene black) were added to prepare a paste-like positiveelectrode composite material. At this time, each material was weighed soas to obtain a solid content of 56 wt %, and mixing was performed usinga planetary mixer. The mass ratios of the positive electrode activematerial, conductive aid, binder, and dispersant contained in thepositive electrode composite material were set to 80:8:2:0.2.

Next, the positive electrode composite material was applied to bothsurfaces of a sheet-shaped positive electrode current collector(aluminum foil) by using a die coater and dried, and then pressed at apredetermined pressure to produce a sheet-shaped positive electrode inwhich the positive electrode composite material was applied to thepositive electrode current collector.

(b) Production of Negative Electrode

A negative electrode was produced using a natural graphite material(graphite) having an average particle diameter of 20 μm as a negativeelectrode active material in each of Test Examples 1 to 5. Specifically,a negative electrode active material, a binder (SBR: styrene-butadienecopolymer), and a thickener (CMC) were mixed in a dispersion solvent(water) to prepare a paste-like negative electrode composite material.This negative electrode composite material was applied to both surfacesof a sheet-shaped negative electrode collector (copper foil), and dried,and then pressed to produce a sheet-shaped negative electrode. Themixing ratios of the negative electrode active material, SBR, and CMC inthe above-described negative electrode composite material were adjustedto 98:1:1.

(c) Production of Battery

Next, the positive electrode and the negative electrode described abovewere laminated with a sheet-shaped separator interposed therebetween,and the laminate was thereafter wound to produce a flat wound electrodebody. A lithium ion secondary battery for evaluation tests wasconstructed by connecting the produced wound electrode body to theexternal terminals of a case, housing together with the electrolyte inthe case and sealing. As the electrolyte, a non-aqueous electrolyticsolution was used in which LiPF₆ as a supporting salt was contained at aconcentration of about 1 mol/liter in a mixed solvent including EC, DMC,and EMC at volume ratios of 1:1:1.

(3) Evaluation Test

In the present test example, a battery resistance evaluation test wasperformed on lithium ion secondary batteries for evaluation tests ofTest Examples 1 to 5. In addition, in the present test example, theactivation process of the lithium ion secondary battery as an evaluationobject was performed before the below-described evaluation test.Specifically, after charging up to 4.2 V by constant-current charging inwhich the current value was set to ⅓ C, constant-voltage charging wasperformed until the current value became 1/50 C, and a fully chargedstate was achieved. Then, constant-current discharging in which thecurrent value was set to ⅓ C was performed to 3 V, and the capacitanceat this time was taken as the initial capacitance. The temperature inthis activation treatment was set to 25° C.

In this test example, the “normalized resistance value” was measured toevaluate the battery resistance of each test example. Specifically,first, the open circuit voltage for each evaluation test was adjusted to3.70 V corresponding to 56% of SOC (State of Charge). Then, each batterywas placed under a temperature condition of 25° C., and constant-currentdischarging was performed until the voltage between the terminals became3.00 V. The voltage between the terminals and the electric current valuein 5 sec after the start of discharging were measured, and theresistance value calculated based on the measurement result was taken asthe “normalized resistance value”. The calculation results are shown inTable 1. The “normalized resistance value” in Table 1 is shown by thelogarithm for which the measurement result of Test Example 4 was takenas 100.

TABLE 1 Structure of conductive oxide Normalized Test ConductiveParticulate Film-shaped Coverage resistance example Active materialoxide region region (%) value 1 LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ RuO₂Present Present 11 75 2 LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ RuO₂ Absent Present11 92 3 LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ RuO₂ Present Absent 11 90 4LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ — Absent Absent — 100 5LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ LaMn_(0.5)Co_(0.5)O₃ Present Present 11 77

(4) Test Results

From the above test results, it follows that in Test Example 1, thenormalized resistance value was significantly lower than in TestExamples 2 to 4. This result confirmed that by adhering both theparticulate region and the film-shaped region made of RuO₂, which is aconductive oxide represented by the general formula: MO₂, to the surfaceof the positive electrode active material, an appropriate electron pathis formed between the positive electrode active material and theconductive oxide and sufficient contact area between the positiveelectrode active material and the electrolyte is ensured, thereby makingit is possible to construct a high-performance lithium ion secondarybattery.

Further, the result that the normalized resistance value was reduced tothe same degree as in Test Example 1 was also obtained in Test Example5. This result has confirmed that a high-performance lithium ionsecondary battery can also be obtained by using a conductive oxiderepresented by the general formula ABO₃, such as LaMn_(0.5)Co_(0.5)O₃,instead of the conductive oxide represented by the general formula MO₂,such as RuO₂, and causing, both the particulate region and thefilm-shaped region composed of the conductive oxide of such acomposition to adhere to the surface of the positive electrode activematerial.

2. Test B

A test B was conducted to investigate the effect produced on batteryperformance by the coverage of the conductive oxide on the surface ofthe positive electrode active material when both the particulate regionand the film-shaped region composed of the conductive oxide are causedto adhere to the surface of the positive electrode active material.

In Test B, as shown in Table 2 below, the normalized resistance valuewas measured for lithium ion secondary batteries (Test Examples 6 to 9)constructed under the same conditions as in Test Example 1 of Test A,except that the coverage of the conductive oxide was varied. In Table 2below, the results of Test Examples 1 and 4 in Test A are also describedas comparative controls.

TABLE 2 Structure of Composition of conductive oxide Normalized Testconductive Particulate Film-shaped Coverage resistance example Activematerial oxide region region (%) value 1 LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂RuO₂ Present Present 11 75 4 LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ — AbsentAbsent — 100 6 LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ RuO₂ Present Present 32 71 7LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ RuO₂ Present Present 40 73 8LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ RuO₂ Present Present 0.9 83 9LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ RuO₂ Present Present 51 81

As shown in Table 2, in Test Examples 1 and 6 to 9, a decrease in thenormalized resistance value was confirmed, and among these, thenormalized resistance value in Test Examples 1, 4 and 7 has decreasedmore significantly. This result has confirmed that when both theparticulate region and the film-shaped region composed of the conductiveoxide are caused to adhere to the surface of the positive electrodeactive material, the coverage of the conductive oxide is preferably 0.9%to 51%, and more preferable 11% to 40%.

3. Test C

Next, Test C was conducted to investigate the effect produced on batteryperformance by the average particle diameter of the particulate regionof the conductive oxide and the film thickness of the film-shaped regionwhen both the particulate region and the film-shaped region composed ofthe conductive oxide are caused to adhere to the surface of the positiveelectrode active material.

In Test C, as shown in Table 3 below, the normalized resistance valuewas measured for lithium ion secondary batteries (Test Examples 10 to16) constructed under the same conditions as in Test Example 6 of TestB, except that the average particle diameter of the particulate regionand the film thickness of the film-shaped region were varied.

TABLE 3 Average Structure of particle Film conductive oxide diameter ofthickness of Normalized Test Particulate Film-shaped particulatefilm-shaped Coverage resistance example region region region (nm) region(nm) (%) value 10 Present Present 0.6 0.5 32 74 11 Present Present 23 2532 71 12 Present Present 55 50 32 72 13 Present Present 23 0.2 32 83 14Present Present 23 55 32 82 15 Present Present 0.3 25 32 80 16 PresentPresent 60 25 32 80

As shown in Table 3, a decrease in the normalized resistance value wasconfirmed in any of Test Examples 10 to 16, but a more significantdecrease in the normalized resistance value was confirmed in TestExamples 10 to 12. This result has confirmed that a lithium ionsecondary battery having better battery performance can be constructedby setting the average particle diameter of the particulate region inthe range of 0.6 nm to 55 nm and setting the film thickness of thefilm-shaped region in the range of 0.5 nm to 50 nm.

The present invention has been described hereinabove in detail, but theabove-described embodiments are merely exemplary, and the inventiondisclosed herein includes various modifications and alterations of thespecific examples described above.

Further, since the lithium ion secondary battery provided by thetechnique disclosed herein exhibits, as described above, excellentbattery performance, the battery can be advantageously used, forexample, as a power source for a motor (electric motor) mounted on avehicle such as an automobile. Moreover, such lithium ion secondarybatteries may be used in the form of a battery pack formed by connectinga plurality thereof in series and/or in parallel. Therefore, accordingto the technique disclosed herein, it is possible to provide a vehicle(typically, an automobile, in particular an automobile provided with anelectric motor, such as a hybrid automobile, an electric automobile, anda fuel cell automobile) equipped with a lithium ion secondary battery,or a battery pack including a plurality of such batteries, as a powersource.

REFERENCE SIGNS LIST

-   1 Positive electrode active material-   2 a Particulate area-   2 b Film-shaped region-   10 Positive electrode-   12 Positive electrode current collector-   14 Positive electrode composite material layer-   16 Positive electrode composite material layer non-formation portion-   20 Negative electrode-   22 Negative electrode current collector-   24 Negative electrode composite material layer-   26 Negative electrode composite material layer non-formation portion-   40 Separator-   50 Case-   52 Case body-   54 Lid-   70 Positive electrode terminal-   72 Negative electrode terminal-   80 Wound electrode body-   100 Lithium ion secondary battery

The invention claimed is:
 1. A positive electrode composite material fora lithium ion secondary battery, the positive electrode compositematerial comprising: a particulate positive electrode active materialcomposed of a lithium composite oxide having a layered crystal structureincluding at least lithium, and a conductive oxide, wherein aparticulate region where primary particles of the conductive oxide areaggregated, and a film-shaped region where the conductive oxide isformed in a film shape adhere to at least a part of the surface of thepositive electrode active material, an average particle diameter ofprimary particles in the particulate region based on cross-sectional TEMobservation is equal to or greater than 0.3 nm, and in cross-sectionalTEM observation of the film-shaped region, no particles with a particlediameter equal to or greater than 0.3 nm are observed, and there are novoids equal to or greater than 2 nm.
 2. The positive electrode compositematerial for a lithium ion secondary battery according to claim 1,wherein the conductive oxide is a metal oxide represented by a generalformula (1):MO₂  (1) (where, M in the formula (1) above is one or two or moreelements selected from transition metal elements of groups Va, VIa,VIIa, VIII, and Ib), or a metal oxide having a perovskite structure andrepresented by a general formula (2):ABO₃  (2) (where, A in the formula (2) above is one or two or moreelements selected from the group consisting of divalent typicalelements, lanthanoid elements, and a combination thereof, and B is oneor two or more elements selected from transition metal elements ofgroups IVa, Va, VIa, VIIa, VIII, and Ib).
 3. The positive electrodecomposite material for a lithium ion secondary battery according toclaim 2, wherein the conductive oxide is ruthenium oxide or a lanthanummanganese cobalt composite oxide.
 4. The positive electrode compositematerial for a lithium ion secondary battery according to claim 1,wherein the positive electrode active material is a lithium compositeoxide represented by a general formula (3):Li_(1+α)Ni_(x)Co_(y)Mn_(z)M_(β)O_(2−γ)A_(γ)  (3) (where, M in theformula (3) above is one or two or more elements selected from the groupconsisting of Zr, Mo, W, Mg, Ca, Na, Fe, Cr, Zn, Si, Sn, Al, and B; A inthe formula (3) is one or two or more elements selected from the groupconsisting of F, Cl, and Br; and x, y, z, α, β, and γ is 0≤α≤0.7,0≤x<0.9, 0≤y<0.4, 0≤β≤0.1n 0.1≤γ≤0.5, respectively).
 5. The positiveelectrode composite material for a lithium ion secondary batteryaccording to claim 1, wherein a coverage based on cross-sectional TEMobservation of the conductive oxide on the surface of the positiveelectrode active material is 11% to 40%.
 6. The positive electrodecomposite material for a lithium ion secondary battery according toclaim 1, wherein an average particle diameter based on cross-sectionalTEM observation of the particulate region is 0.6 nm to 55 nm, and a filmthickness based on cross-sectional TEM observation of the film-shapedregion is 0.5 nm to 50 nm.
 7. The positive electrode composite materialfor a lithium ion secondary battery according to claim 1, wherein atleast parts of the particulate region and the film-shaped region are incontact with each other.
 8. A lithium ion secondary battery comprising:a positive electrode having a positive electrode composite materiallayer applied to a positive electrode current collector; a negativeelectrode having a negative electrode composite material layer appliedto a negative electrode current collector; and a non-aqueouselectrolyte, wherein the positive electrode composite material layerincludes a particulate positive electrode active material composed of alithium composite oxide having a layered crystal structure including atleast lithium, and a conductive oxide, a particulate region whereprimary particles of the conductive oxide are aggregated, and afilm-shaped region where the conductive oxide is formed in a film shapeadhere to at least a part of the surface of the positive electrodeactive material, an average particle diameter based on cross-sectionalTEM observation of primary particles in the particulate region is equalto or greater than 0.3 nm, and in cross-sectional TEM observation of thefilm-shaped region, no particles with a particle diameter equal to orgreater than 0.3 nm are observed, and there are no voids equal to orgreater than 2 nm.